Hydrofluorocarbons ("HFC's") are of great interest due to their potential to replace ozone-depleting chlorofluorocarbons ("CFC's") and hydrochlorofluorocarbons ("HCFC's") in a variety of applications including refrigerant, solvent, foam blowing, aerosol propellant, and heat transfer applications. Among the HFC's, 1,1,1,3,3-pentafluoropropane ("HFC-245fa") has been identified as a foam blowing agent, an aerosol propellant, and a heat transfer agent as well as a possible replacement for dichlorodifluoromethane in refrigeration systems.
Methods for the preparation of HFC-245fa are known. For example, the catalytic hydrogenation of 1,1,1,3,3-pentafluoropropene with hydrogen in the presence of a palladium catalyst is disclosed in WO 94/29251. Hydrodechlorination of 3-chloro-1,1,1,3,3-pentafluoropropane with hydrogen over a reduction catalyst to produce HFC-245fa is disclosed in WO 95/04022. The preparation of HFC-245fa from di- or trichloropentafluoropropanes via hydrogenation is disclosed in EP 611 744. The reaction of vinyl chloride with carbon tetrachloride to produce CCl.sub.3 CH.sub.2 CHCl.sub.2 ("HCC-240fa") followed by the fluorination of HCC-240fa with hydrogen fluoride in the presence of a fluorination catalyst to produce HFC-245fa is disclosed in U.S. Pat. No. 5,574,192. U.S. Pat. No. 5,616,819 discloses the uncatalyzed fluorination of a chlorinated olefin followed by the catalyzed fluorination of the resulting chlorofluoro intermediate to produce HFC-245fa.
Certain disadvantages are inherent in all of these methods. The hydrogenation of unsaturated pentafluoropropene and mono-, di-, and trichloropentafluoropropanes requires either or both high reaction temperatures and multiple steps to prepare the feed material. Additionally, the reaction exhibits poor selectivity for the desired product. The fluorination of HCC-240fa with an antimony pentafluoride fluorination catalyst is highly corrosive to metallic reactors. The fluorination of chlorinated olefins in the presence of catalysts produces a tarry residue and the desired product is formed in poor yields.
Therefore, a need exists in the art for new methods for producing HFC-245fa that overcomes some of these disadvantages.